From a31f6b6f206b0b07e889de01808eff00d905ab4f Mon Sep 17 00:00:00 2001
From: maxnawa31 <mnawa31@gmail.com>
Date: Tue, 9 Oct 2018 14:29:17 -0700
Subject: [PATCH 1/2] reverse polish notation in progress

---
 Evaluate-Reverse-Polish-Notation/README.md    | 38 ++++++++++++++++
 Evaluate-Reverse-Polish-Notation/index.js     |  4 ++
 .../index.test.js                             | 41 ++++++++++++++++++
 Evaluate-Reverse-Polish-Notation/solution.js  | 43 +++++++++++++++++++
 4 files changed, 126 insertions(+)
 create mode 100644 Evaluate-Reverse-Polish-Notation/README.md
 create mode 100644 Evaluate-Reverse-Polish-Notation/index.js
 create mode 100644 Evaluate-Reverse-Polish-Notation/index.test.js
 create mode 100644 Evaluate-Reverse-Polish-Notation/solution.js

diff --git a/Evaluate-Reverse-Polish-Notation/README.md b/Evaluate-Reverse-Polish-Notation/README.md
new file mode 100644
index 0000000..a5aa451
--- /dev/null
+++ b/Evaluate-Reverse-Polish-Notation/README.md
@@ -0,0 +1,38 @@
+# Evaluate Reverse Polish Notation
+
+Write a method called `evalRPN` that evaluates the value of an arithmetic expression in Reverse Polish Notation.
+
+Valid operators are +, -, \*, /. Each operand may be an integer or another expression.
+
+Notes:
+
+- Division between two integers should truncate toward zero (negative numbers should be rounded towards zero, and positive numbers should be rounded towards zero)
+- The given RPN expression is always valid. That means the expression would always evaluate to a result and there won't be any divide by zero operation.
+- [Link to Wikipedia's explanation on Reverse Polish Notation](https://en.wikipedia.org/wiki/Reverse_Polish_notation)
+
+Example:
+
+```js
+Input:  ["2", "1", "+", "3", "*"];
+Output: 9;
+Explanation: ((2 + 1) * 3) = 9
+```
+
+```js
+Input: ["4", "13", "5", "/", "+"];
+Output: 6;
+Explanation: (4 + (13 / 5)) = 6
+```
+
+```js
+Input: ["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"]
+Output: 22
+Explanation:
+  ((10 * (6 / ((9 + 3) * -11))) + 17) + 5
+= ((10 * (6 / (12 * -11))) + 17) + 5
+= ((10 * (6 / -132)) + 17) + 5
+= ((10 * 0) + 17) + 5
+= (0 + 17) + 5
+= 17 + 5
+= 22
+```
diff --git a/Evaluate-Reverse-Polish-Notation/index.js b/Evaluate-Reverse-Polish-Notation/index.js
new file mode 100644
index 0000000..75c9742
--- /dev/null
+++ b/Evaluate-Reverse-Polish-Notation/index.js
@@ -0,0 +1,4 @@
+function evalRPN(tokens) {
+
+}
+export default evalRPN;
\ No newline at end of file
diff --git a/Evaluate-Reverse-Polish-Notation/index.test.js b/Evaluate-Reverse-Polish-Notation/index.test.js
new file mode 100644
index 0000000..08a5b85
--- /dev/null
+++ b/Evaluate-Reverse-Polish-Notation/index.test.js
@@ -0,0 +1,41 @@
+const {
+  evalRPN
+} = require('./solution');
+
+describe("evalRPN", () => {
+  it("Returns an integer", () => {
+    const tokens = ["2", "1", "+", "3", "*"]
+    const result = evalRPN(tokens);
+    expect(typeof (result)).toBe('number');
+  });
+
+  it("Truncates division between two integers toward zero when negative", () => {
+    const tokens = ["2", "-123", "/"];
+    const result = evalRPN(tokens);
+    expect(result).toEqual(0);
+  })
+
+  it("Truncates division between two integers toward zero when positive", () => {
+    const tokens = ["4", "3", "/"];
+    const result = evalRPN(tokens);
+    expect(result).toEqual(1);
+  });
+
+  it("Evaluates correctly", () => {
+    const tokens = ["2", "1", "+", "3", "*"];
+    const result = evalRPN(tokens);
+    expect(result).toEqual(9)
+  })
+
+  it("Evaluates correctly", () => {
+    const tokens = ["4", "13", "5", "/", "+"];
+    const result = evalRPN(tokens);
+    expect(result).toEqual(6)
+  })
+
+  it("Evaluates correctly", () => {
+    const tokens = ["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"];
+    const result = evalRPN(tokens);
+    expect(result).toEqual(22)
+  })
+})
\ No newline at end of file
diff --git a/Evaluate-Reverse-Polish-Notation/solution.js b/Evaluate-Reverse-Polish-Notation/solution.js
new file mode 100644
index 0000000..06df1f5
--- /dev/null
+++ b/Evaluate-Reverse-Polish-Notation/solution.js
@@ -0,0 +1,43 @@
+function evalRPN(tokens) {
+  let stack = [];
+  let total;
+  let operators = {
+    "+": function (a, b) {
+      return a + b
+    },
+    "-": function (a, b) {
+      return a - b
+    },
+    "*": function (a, b) {
+      return a * b
+    },
+    "/": function (a, b) {
+      let number = a / b
+      let quotient = Math[number < 0 ? 'ceil' : 'floor'](number);
+      if (quotient === -0) {
+        return 0
+      } else {
+        return quotient
+      }
+    }
+  }
+
+  if (tokens.length === 1) {
+    return parseInt(tokens[0]);
+  }
+  for (let i = 0; i < tokens.length; i++) {
+    if (tokens[i] in operators) {
+      let second = stack.pop();
+      let first = stack.pop();
+      let amount = operators[tokens[i]](first, second);
+      stack.push(amount);
+    } else {
+      stack.push(parseInt(tokens[i]));
+    }
+  }
+  return stack.pop();
+};
+
+module.exports = {
+  evalRPN
+}
\ No newline at end of file

From a848e6374e66caa083bdfa4bc51cf51c989b27a2 Mon Sep 17 00:00:00 2001
From: maxnawa31 <mnawa31@gmail.com>
Date: Tue, 9 Oct 2018 14:35:16 -0700
Subject: [PATCH 2/2] finished reverse polish notation, ready for pull request

---
 Evaluate-Reverse-Polish-Notation/README.md     |  2 ++
 Evaluate-Reverse-Polish-Notation/index.js      |  5 ++++-
 Evaluate-Reverse-Polish-Notation/index.test.js | 14 ++++++++++----
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/Evaluate-Reverse-Polish-Notation/README.md b/Evaluate-Reverse-Polish-Notation/README.md
index a5aa451..9b5931d 100644
--- a/Evaluate-Reverse-Polish-Notation/README.md
+++ b/Evaluate-Reverse-Polish-Notation/README.md
@@ -36,3 +36,5 @@ Explanation:
 = 17 + 5
 = 22
 ```
+
+Companies that have asked this question: -
diff --git a/Evaluate-Reverse-Polish-Notation/index.js b/Evaluate-Reverse-Polish-Notation/index.js
index 75c9742..78e156d 100644
--- a/Evaluate-Reverse-Polish-Notation/index.js
+++ b/Evaluate-Reverse-Polish-Notation/index.js
@@ -1,4 +1,7 @@
 function evalRPN(tokens) {
 
 }
-export default evalRPN;
\ No newline at end of file
+
+module.exports = {
+  evalRPN
+}
\ No newline at end of file
diff --git a/Evaluate-Reverse-Polish-Notation/index.test.js b/Evaluate-Reverse-Polish-Notation/index.test.js
index 08a5b85..4f79987 100644
--- a/Evaluate-Reverse-Polish-Notation/index.test.js
+++ b/Evaluate-Reverse-Polish-Notation/index.test.js
@@ -1,6 +1,6 @@
 const {
   evalRPN
-} = require('./solution');
+} = require('./index');
 
 describe("evalRPN", () => {
   it("Returns an integer", () => {
@@ -21,21 +21,27 @@ describe("evalRPN", () => {
     expect(result).toEqual(1);
   });
 
-  it("Evaluates correctly", () => {
+  it("Evaluates correctly for ['2', '1', '+', '3', '*']", () => {
     const tokens = ["2", "1", "+", "3", "*"];
     const result = evalRPN(tokens);
     expect(result).toEqual(9)
   })
 
-  it("Evaluates correctly", () => {
+  it("Evaluates correctly for ['4', '13', '5', '/', '+']", () => {
     const tokens = ["4", "13", "5", "/", "+"];
     const result = evalRPN(tokens);
     expect(result).toEqual(6)
   })
 
-  it("Evaluates correctly", () => {
+  it("Evaluates correctly for ['10', '6', '9', '3', '+', '-11', '*', '/', '*', '17', '+', '5', '+']", () => {
     const tokens = ["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"];
     const result = evalRPN(tokens);
     expect(result).toEqual(22)
+  });
+
+  it("Returns integer if tokens have length of 1", () => {
+    const tokens = ["13"];
+    const result = evalRPN(tokens);
+    expect(result).toEqual(13);
   })
 })
\ No newline at end of file